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mineral data
Mineral Name: garnet
Gem Names: almandite - spessartite - tsavorite - grossular - uvarovite - pyrope -rhodolite
Chemistry: X3Y2(SiO4)3
where X can be (Fe2+, Mg 2+, Ca 2+, or Mn 2+ )
where Y can be (Al3+, Fe3+ or Cr3+ )
Class: silicates (neosilicates)
Crystal Sys: isometric
Hardness: 6.5 - 7.5 Specific Gravity: 3.58 - 4.32
Dispersion: almanditte: 0.027
rhodolite: 0.022
pyrope: 0.022
spessartite: 0.027
grossular: 0.020
tsavorite: 0.020
andradite: 0.057
uvarovite: 0.014 - 0.021
 Refractive Index: almanditte: 1.77 - 1.82
rhodolite: 1.77 - 1.82
pyrope: 1.72 - 1.756
spessartite: 1.79 - 1.82
grossular: 1.734 - 1.76
tsavorite: 1.73 - 1.76
andradite: 1.88 - 1.94
uvarovite: 1.87
Fracture: conchodial
Misc Prop: Garnet is the generic term for a family of minerals that share a similar formula and the same crystal structure. Most of the garnets are not pure, they have slight variations in formula and can be defined into smaller groups with two "end-members". The end members have specific formulas. but the actual stones have a mixture of the two end member formulas.

Pyrope garnet Mg3Al2(SiO4)3 and Almandite garnet Fe3Al2(SiO4)3 form one such series of garnets. Rhodolite garnet is a member of this chain roughly half way between the two end members. (Mg1.5, Fe1.5) Al2(SiO4)3 . All of these garnets are in the red/violet - red/brown color spectrum.

Spessartite garnet in the manganese analog Mn3Al2(SiO4)3 and is in the red-orange to red-brown color area.

Grossular garnets are the calcium rich varieties. Ca3Al2(SiO4)3 There are several garnets with this general formula, hessonite, hydrogrossular, and the best known tsavorite. Tsavorite is a bright green and very right garnet that can be confused for emerald in smaller stones.

Andradite garnets Ca3Fe2(SiO4)3 have a very high dispersion and refractive index and produce "diamond-like" stones. This series produces beautiful stones but rarely in the larger sizes. Melanite is a black variety and topazolite is a yellow variety. The Demantoid is the most prized and is another bright green variety.

Uvarovite is the chromium - calcium garnet Ca3Cr2(SiO4)3 and this garnet could be a real winner if it were ever found in larger sizes. Typically it found as 1-2 mm crystal coverings. It is very rarely fond large enough to facet. It is a beautiful green color but almost unknown in the jewelry trade. It can be found sometimes as a "drusy" coating and cut as a flat cabochon displaying the small crystals.
Color: In gemstones, color, is often the key to naming or describing the particular variety. Hence look for this information below in the various descriptions. Color, opacity, and homogeneity often determine the placement of value on any given stone, and are all optical properties of the particular stone.
Specific Images:
round stone in the brown-red color range
cushion cut with a red-violet color
round native cut oragne stone
triangular shield cut stone
small triangular cut stone with grape color
strange cut stone in the orange-red color
round stone with nice traditional rhodolite color
long rectangular stone with wine red color
oval spessartite with poor native cut
oval orange color but again poor native cut
small round with lighter yellow-orange color - better native cut
hessonite (brown-orange) color, square cut with flaw
nice native cut triangular stone with good color.
small round cut stone with good color
mixed cut design with good color